21728319915 has 32 divisors (see below), whose sum is σ = 36674668800. Its totient is φ = 10954638720.

The previous prime is 21728319887. The next prime is 21728319929. The reversal of 21728319915 is 51991382712.

It is a happy number.

It is not a de Polignac number, because 21728319915 - 2²⁰ = 21727271339 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 48696 + ... + 214074.

It is an arithmetic number, because the mean of its divisors is an integer number (1146083400).

Almost surely, 2^21728319915 is an apocalyptic number.

21728319915 is a deficient number, since it is larger than the sum of its proper divisors (14946348885).

21728319915 is a wasteful number, since it uses less digits than its factorization.

21728319915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165867.

The product of its digits is 272160, while the sum is 48.

The spelling of 21728319915 in words is "twenty-one billion, seven hundred twenty-eight million, three hundred nineteen thousand, nine hundred fifteen".